1. Field of the Invention
The present invention relates to an external combustion engine using evaporation and condensation of a working fluid to cause a liquid phase part of a working fluid to displace, and converting the displacement of the liquid phase part of the working fluid to mechanical energy for output.
2. Description of the Related Art
This type of external combustion engine is called a “liquid piston steam engine”. In this conventional type of engine, a pipe-shaped container is sealed with a working fluid flowable in a liquid state, a heated part formed at one end of the container is used to heat part of the liquid state working fluid to cause it to evaporate, and a cooled part formed at the middle of the container is used to cool the vapor of the working fluid to cause it to condense. By alternately repeating evaporation and condensation of this working fluid, the liquid phase part of the working fluid is cyclically made to displace (so-called “self-excited vibration”), then this self-excited vibration of the liquid phase part of the working fluid is taken out at an output unit as mechanical energy. (For example, see Japanese Patent Publication (A) No. 2004-84523 and Japanese Patent Publication (A) No. 2007-255259).
In the engine disclosed in Japanese Patent Publication (A) No. 2007-255259, the internal pressure of the container is regulated in accordance with the temperature of the heated part to improve the efficiency of the liquid piston steam engine. Note that in the engine disclosed in Japanese Patent Publication (A) No. 2004-84523, the internal pressure of the container is not regulated.